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É"enne Boucher Taha B.M. J. Ouarda
Yves Bégin Antoine Nicault
Ins<tut Na<onal de la Recherche Scien<fique Centre Eau-‐Terre-‐Environnement
Photo credit: S. Popov World Dendro 2010, Rovaniemi, Finland
Why reconstruct spring floods?
Hudson bay
LA GRANDE (LG) hydroelectric complex
Why reconstruct spring floods?
Pros
Cons
A mul<-‐proxy dendrohydrological approach to reconstruct spring floods
Discon<nuous series / uncertain<es / non-‐lineari<es
Direct rela<onship with streamflow Con<nuous series
Indirect rela<onships with
streamflow
Discrete event series e.g. ice scarred trees
Uncertain discrete series
[0.05, 0.5, 0.95]
Propor<on of ice-‐scarred trees around a northern lake
Prop
or<o
ns
N trees sampled
Model uncertain"es of discrete event series Uncertain<es around observed propor<ons are binomialy distributed 1)
Model verifica"on Jackknife resampling 3)
Calibra"on / Reconstruc"ons Performed using Generalized Addi<ve Models (GAMs) 2)
€
g(E(Q)) = B0 + f1TR1 + f2TR2 + ...
Reconstruc<on of May water supplies to the Caniapiscau reservoir (northern Québec, Canada)
Hudson bay
La Grande HE complex
Dendrochronological data
= Earlywood density = Ice scar chronology at lake Montausier
Water supplies to the Caniapiscau reservoir, & hydrological variables to reconstruct
Discrete and con<nuous dendroseries
Propor<on of ice scoured trees around lake Montausier
Earlywood density, PC1
Earlywood density, PC2
The Montausier lake ice scar chronology (an other look at it…)
Prop
or<o
ns
N=300
For each year, N=300 possible propor<ons were randomly generated from a binomial distribu<on.
Colors indicate « the number of "mes a simulated propor<on value falls in each class »
Rela<onships between TR series & water supplies (QMay) to the Caniapiscau Reservoir
Propor<ons of ice scarred trees, Montausier lake
PC1 Index
(wet sites)
PC2 index
(mesic xeric sites)
Calibra<on / verifica<on sta<s<cs & comparison with a tradi<onal MLR approach
€
g(E(QMay )) = B0 + f1X1 + f2X2 + ...
€
E(QMay ) = B0 + B1X1 + B2X2 + ...
+
Discussion and Conclusion
-‐ A new approach to reconstruct paleofloods from tree rings in northern environment. It allows:
1) to take advantage of both discrete and con"nuous tree ring proxys
2) to model and include the uncertainty of discrete TR series within the calibra<on / reconstruc<on process
3) to account for non-‐linear rela"onships that occur in natural environments
-‐ Our approach can be used in other environments / situa<ons where discrete and con<nuous tree ring series are available
BIENVILLE MONTAUSIER
CORVETTE
LEC
NECOPASTIC
HERVÉ
POLARIS
